Regulating device on a grinding arrangement



Dec. 9, 1969 v A. SCHMID ET AL 3,482,787

REGULATING DEVICE ON A GRINDING ARRANGEMENT Original Filed Jan. 16, 1967 4 Sheets-Sheet 1 INVENTORS Alfred Sc/wm'd Heinz NyFfenegger Hansrudo/F Brunt A T TORNE Y5 Dec. 9, 1969 A, SCHMID ET AL 3,482,787 REGULATING DEVICE ON A GRINDING ARRANGEMENT I Original Filed Jan. 16, 1967 4 Sheets-Sheet ,2

nvvszvroks A/Fred SChm-Ld Heinz NyFFenegger Hahsruc/o/F BrunL ATTORNEYS Dec. 9, 1969 A, SCHMID ET AL REGULATING DEVICE ON A GRINDING ARRANGEMENT Originl Filed Jan. 16, 1967 4 Sheets-Sheet 3 INVENTORS A/f/ed 5c/7mllc/ Heinz Nyl fenegger Hansruoo/F 5mm BY AT70RNEY5 Dec. 9, 1969 scHmp ET AL 3,482,787

REGULATING DEVICE ON A GRINDING ARRANGEMENT Original Filed Jan. 16, 1967 4 Sheets-Sheet 4 l 211 F ,212 z I 204i 210 L 205I I 103 215 203 I E f V/ A L. 199 220} 221 M1 I 7 2 218 I 1 .2Q

l 4 l l 1 FT 222 2 fi k 99 1226 INVENTORS' A/Freo Schmid Heinz Nyffenegger Hansrudo/F Bruni ATTORNEYS United States Patent U.S. Cl. 241-34 7 Claims ABSTRACT OF THE DISCLOSURE In a grinding arrangement, a regulating device with an apparatus for measuring the permeability of samples of the finished product. A prescribed quantity of measuring gas flows through a sample and displaces a corresponding quantity of measuring liquid. A timing means measures the time for the displacement of the liquid and converts the result into a signal corresponding to the specific surface of the sample. This signal controls a device for influencing the degree of grinding of the grinding arrangement.

This application is a continuation of our application Ser. No. 609,508, filed Jan. 16, 1967, now abandoned.

This invention relates to a regulating device on a grinding arrangement for maintaining a prescribed specific surface of the finished product, comprising a permeability measuring arrangement for measuring the specific surface of the ground product which is formed. The grinding arrangement includes a permeability cell with a cylinder through which measuring gas flows and two gas-permeable screen plates which are substantially perpendicular to the cylinder axis and which, for compressing a pellet of test material, are constructed so that they are movable relatively to one another into a filling position and also into a pressing position of prescribed distance from one another. In pressing positions they axially define a pellet chamber of prescribed volume and are adapted to be secured in these pressing positions. The space situated on that side of one of the screen plates which is remote from the pellet chamber is connected to a measuring gas connection. One of the screen plates is in addition constructed to be movable into a withdrawal position freeing that end of the cylinder which is. associated with it. A quantity meter is connected by way of a measuring gas pipe provided with a measuring gas valve to the measuring gas connection of the permeability cell. The quantity meter comprises a gas zone and contains measuring liquid, and is used to determine the quantity of the measuring gas flowing through the permeability cell by means of liquid displacement. The gas zone of said quantity meter is adapted to be connected to a device for producing a vacuum, and also with a device for influencing the degree of grinding of the grinding arrangement.

Such arrangements are used in numerous branches of industry, more especially in the cement industry, in the dressing of ores, in the ceramic industry and similar fields.

The measurement of the specific surface of the ground product of a grinding arrangement is important not only for checking the quality but more especially also for the control of the grinding operation so that this can be carried out economically. A grinding to a finer degree than that which is required consumes ineffectively driving energy for the grinding arrangement. As a result, it is desirable to be able to measure the specific surface of the ground product being formed in a close time sequence 3,482,787 Patented Dec. 9, 1969 and in this way to obtain measurement results which render possible a direct control of the device which influences the grinding operation. It is quite clear that the most economical way of operating the grinding operation would be obtained with an automated regulating device.

As is known, with grinding arrangements operating in an open cycle, the grinding operation is influenced by the actuation of the device for dosing the supplied material. In grinding arrangements operating in a closed cycle, in which the output of the grinding arrangement is connected to the inlet of a sitting device comprising a means for regulating the degree of sifting, and in which the coarse material outlet of said sifting device is connected to the inlet of the grinding arrangement, the grinding operation is influenced by actuating said means for regulating the degree of sitting. The grinding operation can also be influenced by actuating a speed-control device on the driving means for the grinding arrangement or, with grinding arrangements comprising movable grinding bodies, by actuating a control means of a device for increasing the friction of the grinding bodies relatively to the grinding walls of the grinding arrangement. A direct control of these known devices for influencing the grinding operation of the grinding arrangement is however impossible by means of the prior known permeability measuring device.

As explained in co-pending application Ser. No. 592,- 115, filed Nov. 4, 1966, now Patent No. 3,433,056, and belonging to applicants assignee, in permeability cells known prior to that application the pellet compressed from test material is removed by being blown out by means of compressed air after having completed the permeability measurement. It has been found to be impossible in this way for the test material which is in the cylinder to be completely removed with certainty. Such a pellet residue renders erroneous the measurement results with the following measuring operations, since a larger quantity than corresponds to the prescribed quantity of test material is compressed into a pellet, and this pellet, since a larger quantity of test material is compressed to a prescribed volume, also has a different degree of porosity, i.e. a different ratio between solid volume and total volume. As well as a constant pressure diflerence, a constant quantity of test material and a constant porosity of the pellet constitute a preliminary condition for an accurate and reproducible permeability measurement, which depends on measuring the throughflow time of a prescribed quantity of measuring gas through the pellet. In addition, the known method of removing the pellet from the cylinder causes an undesired dust formation in the surroundings.

As explained in co-pending application Ser. No. 592,- 105, filed Sept. 26, 1966 (now Patent No. 3,420,094), quantity meters known prior to the invention claimed in that application and used for measuring the quantity of the gas flowing through the permeability cell comprise two liquid columns communicating in a U-tube, these columns causing the pressure difference. These arrangements had the defect that the pressure difference effective for the measurement constantly decreases during the measurement. As a consequence, the accuracy of the measurement suffered and above all time-consuming calculations were necessary in order to establish the specific surface of the tested material from the throughflow times for a prescribed gas volume. Another disadvantage of this known arrangement consisted in that the quantity of material which can be examined with each measuring operation was very small and accordingly was not truly representative in every case.

The measurement inaccuracies of these previously known permeability cells and quantity meters were so great in relation to the unavoidable variations during the grinding operation that a direct control of the device influencing the degree of grinding of the grinding arrangement was scarcely possible by means of a permeability measuring arrangement consisting of a known permeability cell and a known quantity meter. More especially a continuous regulation is impossible because those known quantity meters did not supply any measurement results which could be converted directly to the specific surface of the tested material in cm. g. according to Blaine.

The invention has for its object to close this gap and to provide an arrangement for the direct and continuous regulation of the device influencing the degree of grinding of a grinding arrangement in order to Obtain a prescribed specific surface of the ground product. For this purpose the regulating device of the type hereinbefore described, which comprises a permeability measuring arrangement consisting of a permeability cell of the type described and claimed in application Ser. No. 592,115 and also a quantity meter of the type described and claimed in application Ser. No. 582,105, as well as a device for influencing the degree of grinding of the grinding arrangement, is so constructed according to the invention that the following measures are jointly employed:

(a) The other screen plate of the permeability cell is constructed to be movable in a direction towards the pellet chamber, beyond its pressing position and into an ejection position for the purpose of ejecting the pellet from the cylinder.

(b) The quantity meter comprises two measuring liqiud containers containing measuring liquid and arranged one above the other, the upper measuring liquid container being fixed in space, sealed off from the surroundings and connected by its gas zone to the measuring; gas connection of the permeability cell, and the lower measuring liquid container is open at the top and bears on the weighing pan of a balance a measuring liquid pipe connected fast to the upper measuring liquid container opening into said container in the lower region thereof and extending to below the measuring liquid level in the lower measuring liquid container, 3 quantity of measuring liquid corresponding to the gas quantity flowing through the permeability cell, which liquid quantity is displaced by the measuring gas from the upper measuring liquid container, flowing through said measuring liquid pipe into the lower measuring liquid container, while the balance is so designed that the travel of the weighing pan covered under the influence of the weight of the quantity of measuring liquid to be measured is as large as the sum of the fall in the measuring liquid level in the upper measuring liquid container and the simultaneous corresponding rise of the measuring liquid level in the lower measuring liquid container.

(c) A timing means is provided which measures the time within which the indicating element of the balance covers a prescribed distance, which corresponds to a prescribed quantity of measuring liquid and a prescribed quantity of measuring gas flowing through the permeabllity cell, and converts the measurement results into a signal corresponding to the specific surface of the test material pellet traversed by measuring gas.

(d) A control means is provided which is operatively connected on the signal input side to the timing means and on the output side to the device for influencing the degree of grinding of the grinding arrangement, in such a way that when a prescribed time is exceeded by the measured time, the device for influencing the degree of grinding of the grinding arrangement is actuated in the sense for reducing the degree of grinding, whereas when this prescribed time is not reached, the device for influencing the degree of grinding of the grinding arrangement is actuated in the sense for increasing the degree of grinding.

(e) A device for extracting a partial stream is provided after the grinding arrangement, said device following an automatic dosing and weighing device which is connected on the output side to the pellet chamber of the permeability cell.

An embodiment of the invention is shown by Way of 4 example and in simplified form in the drawing wherein:

FIGURE 1 shows a permeability cell of the type described and claimed in application Ser. No. 592,115, partly in section,

FIGURE 2 shows a quantity meter of the type described and claimed in application Ser. No. 582,105, partly in section,

FIGURES 3 and 4 show the quantity meter according to FIGURE 2 in two diflerent operating positions and to a smaller scale, and

FIGURE 5 is a diagram of the regulating device according to the invention on a grinding arrangement with a closed cycle.

The permeability cell and the quantity meter are described in considerable detail in the interest of a full disclosure. Reference may be had to the co-pending applications for any further information necessary to an understanding of this invention.

The permeability cell 99 shown in FIGURE 1 comprises a base plate 1, from which is suspended a vertical, upwardly open cylinder 2, which is closed at the bottom by an end wall 3. Arranged in the lower region of the cylinder 2 is a screen plate 4 which is perpendicular to the cylinder axis and is gas-permeable in the direction of said axis, said screen plate having a large number of uniformly distributed screening apertures 5. Leading from the space beneath the screen plate 4 is a measuring gas connection 6, which is connected by way of a measuring gas pipe (103 in FIGURE 2) to a quantity meter (199 in FIGURE 2) and comprises a measuring gas valve (201 in FIGURE 5), the said measuring gas connection 6 extending outwardly through the end wall 3. Connected to the upwardly open cylinder 2 is a bushing 7, which is closed at the upper end by a cover 8. The bushing 7 is in line with the cylinder 2. Extending through openings (not visible in the drawing) in the cover 8 and in the base plate 1 is a piston rod 9, which carries at its bottom end a screen plate 10 which is gas-permeable in the direction of the cylinder axis and which has a large number of uniformly distributed screening apertures 11. Above the base plate 1, the piston rod 9 extends through a pneumatic servo motor 13 which can be acted upon :at both ends and by means of which the screen plate 10 is movable axially of the cylinder. The screen plate 4 is arranged on the upper end of a piston rod 14, which extends through an opening 15 in the end wall 3 of the cylinder 2 and into a pneumatic servo motor 16 which can be :acted upon at both ends and by means of which the screen plate 4 is movable axially of the cylinder.

In the drawing, the screen plate 4 is shown in its pressing position, which is also its filling position. The screen plate 10 is shown in the drawing in its filling position, which also is its withdrawal position. In this withdrawal position, the screen plate 10 is situated outside the cylinder 2 and trees its associated opening 17 which is at the end opposite to the end wall 3 closing the cylinder at its bottom end, this opening 17 directly adjoining that opening 18 of the bushing 7 which is opposite the cover 8.

The screen plate 10 is movable from its filling and withdrawal position by means of the servo motor 13 into the interior of the cylinder 2 and towards the screen plate 4 to occupy a pressing position. The position of the lower edge of the screen plate 10 in its pressing position is represented by a dash-dotted line 19 in the drawing. When the screen plate 10 is in its pressing position and the screen plate 4 is in its position which is both the filling and pressing position, they are situated at a prescribed distance from one another and thereby axially define a pellet chamber 20 of prescribed volume. The iston rod 9 leads upwardly from the servo motor 13 and is provided at its upper end with a screwthread which carries a stop nut 21 and a locking nut 22. The stop nut 21 and the upper cylinder cover 23 of the servo motor 13 form a stop 21, 23, this stop limiting the movement of the screen plate towards the screen plate 4 and thus establishing the prescribed spacing of the screen plate 10 from the screen plate 4 in the pressing positions of the said two screen plates. The screen plate 10 is adapted to be secured in its pressing position by means of the servo motor 13. The piston rod 9 and thus the screen plate 10 are held fast against rotation relatively to the cylinder 2 by means of a tongue and groove, the groove being arranged inside the servo motor 13 and not being visible in the drawing.

For the ejection of the pellet from the cylinder 2, the screen plate 4 is movable in a direction towards the pellet chamber and beyond its pressing position into an ejection position. In the ejection position of the screen plate 4, the upper edge thereof is disposed in the region of the rim of the opening 17 of the cylinder 2. The movement of the screen plate 4 away from the pellet chamber 20 is limited by a stop 24, which is formed by the servo motor piston 24 and by the lower cylinder cover 25 of the servo motor 16 and in this Way the pressing position of the screen plate 4 is determined. The ejection position of the screen plate 4 is determined in known manner by a stop which is not shown in the drawing and which limits the movement of the servo motor piston 24 towards the end wall 3 of the cylinder 2.

The screen plates 4, 10 each comprise on their surfaces facing the pellet chamber 20 a filter element 26 which is highly gas-permeable, the said filter elements being made of a woven nylon fabric. The filter elements could also be formed as a woven fabric of plastic fibres, as plates of sintered materials and more especially sintered metals or in similar manner. The screen plates 4, 10 are provided on their peripheral surfaces with packings 27.

The bushing 7 comprises a material inlet opening 28 for the material, the said opening extending obliquely downwards and inwardly, a material inlet pipe 29 with a hopper 30 co-operating with said opening.

The cylinder 2 comprises lateral journals 31, 32, which are mounted in bearing heads 33, 34 of piston rods 35, 36 of servo motors 37, 38 which can be acted upon at both ends and are mounted in the base plate 1, the cylinder being turnable about the axes of the journals 31, 32 and being fixedly mounted axially of said journals. The journal 32 carries a worm wheel 39 which is keyed thereon and which is engaged by a Worm 41 mounted in a support fast with the bearing head 34 and fast axially in relation to said support. By means of the servo motors 37, 38, the cylinder 2 can be lowered into a position in which its opening 17 communicates with the surroundings. By means of the worm wheel 39 and the worm 41, the cylinder 2 lowered into the said position can be swung into a substantially horizontal position, in which the pellet can be reliably ejected.

The piston rod 9 is made hollow and the screen plate 10 comprises a corresponding central opening. A stirrer shaft 42 is guided for axial displacement and turning movement inside the piston rod 9, said shaft carrying at its bottom end a stirrer blade 43 taking up approximately the entire diameter of the cylinder 2 and of the bushing 7.

Resting on the base plate 1 is a cylindrical frame 44 which surrounds the servo motor 13 and the piston rod 9, said frame having windows 45 in the axial region of the stop nut 21 and an upper bearer plate 46 which has a central opening 47 receiving the stirrer shaft. Above the bearer plate 46, the stirrer shaft 42 is enclosed by a housing 48 resting on the bearer plate. The stirrer shaft 42 is provided with a screwthread extending from its upper end to below the region of the stop nut. The stirrer shaft is enclosed in the region between the bearer plate 46 and the stop nut 21 by a coupling nut 49 which has an internal thread. This coupling nut 49 comprises a large upper end face, by which it bears in the position shown in the drawing on the bearer plate 46, and

is reduced downwardly, so that it extends with the lower, reduced part into a cylindrical recess in the upper end of the piston rod 9, an annular chamber 50 of small axial size being defined by the piston rod 9, the coupling nut 49 and the stirrer shaft 42. This annular chamber 50 houses a compression spring 51. The piston rod 9 is held fast in rotation relatively to the coupling nut 49 by a pin 52, which pin 52 is movable in a slot 53 which is axially parallel with the piston rod and is of a small axial size, so that the coupling nut can be moved axially by a small amount in relation to the piston rod. The coupling nut 49 carries a downwardly extending pointer 54, the free end of which co-operates with an axial scale 55 of the stop nut 21 and by which the pressing position of the screen plate 10 can be determined.

Above the bearer plate 46, the stirrer shaft 42 is surrounded by a worm wheel 56 bearing with its central bore on the outer surface of the thread of the shaft. This worm wheel is held fast in rotation with the stirrer shaft 42 by means of a key 57 and a key track 58 and is held axially in relation to the bearer plate by means of spacing bushes 59, 60, which rest with their central bores on the outer surface of the threaded profile of the stirrer shaft 42, the key 57 being simultaneously also held axially. Fixed on the side wall of the housing 48 is an electric motor 61 operating at will in either direction of rotation, said motor having a horizontally driven shaft 62, on which is mounted a worm which meshes with the worm wheel 56, the said worm not being visible in the drawing, as it is concealed by the worm Wheel 56. The stirrer shaft 42 carries on its upper end an axially fixed switch cam 63, which cooperates with an upper switch contact 64 and a lower switch contact 65.

Extending through the wall of the bushing 7 is a flushing air pipe 66 which can be connected to a compressed air source (202 in FIGURE 5), the pipe extending into the space between the cover 8 and the screen plate 10. A flushing air pipe 67 which can be connected to a compressed air source also extends through the wall of the cylinder 2 into the space between the end wall 3 and the screen plate 4, a flushing air valve 68 being connected into the said pipe 67.

The permeability cell as illustrated operates as follows. With all the parts in the positions as shown in the drawing, the motor 61 is set in operation in one direction of rotation, the worm wheel 56 being rotated, this rotational movement being transmitted through the key 57 to the stirrer shaft 42. Since the coupling nut 49 surrounding the thread of the stirrer shaft is fast in rotation with respect to the piston rod, the stirrer shaft 42 and the stirrer blade 43 move downwardly, until the switch cam 63 actuates the lower switch contact 65, whereby the motor 61 is stopped. A prescribed and accurately weighed quantity of test material is then introduced into the hopper 30 and passes through the material inlet pipe 29 and the material inlet opening 28 into the space defined by the cylinder 2 and the bushing 7. Throughout the entire time that the prescribed quantity of test material is entering this space, the motor 61 is now operated in the opposite direction of rotation, and the stirrer shaft 42 with the stirrer blade 43 are now rotated in the opposite direction and are moved upwardly. By simplest possible switching measures, it is possible to drive the motor 61 for the downward movement of the stirrer shaft and stirrer blade at twice the speed as compared with the upward movement. The test material entering the space or chamber defined by the cylinder 2 and the bushing 7 is well distributed and largely homogenised by the revolving stirrer blade 43. When the upper position of the stirrer shaft is reached, the switch cam 63 actuates the upper switch contact 64, whereby the motor 61 is stopped.

The screen plate 10 is now moved by means of the servo motor 13 towards the screen plate 4. As a result,

that upwardly directed annular surface of the piston rod 9 which faces the annular chamber 50 is moved away from that annular surface of the coupling nut 49 which faces the annular chamber 50, and the compression spring 51 is detensioned until the pin 52 has reached the upper end of the slot 53. With a further downward movement of the piston rod 9, the coupling nut 49 and with it the stirrer shaft 42 and the stirrer blade 43 are also carried along.

When the stop nut 21 contacts the upper cylinder cover 23 of the servo motor 13, the movement of the screen plate 10 towards the screen plate 4 has ended, and the screen plate 10 is situated in its pressing position as indicated by the dash-dotted line 19, the screen plates 4, 10 axially defining the pellet chamber 20 of prescribed volume. In moving into this pressing position, the screen plate 10 has compressed the initially supplied quantity of test material into a substantially homogeneous pellet of prescribed size. The permeability measurement can now be carried out, and throughout the entire period thereof, the screen plate 10 is held by means of the servo motor 13 in its pressing position. The measuring gas valve (201 in FIGURE 5) in the measuring gas pipe (103 in FIGURE 2) is opened and ambient air flows through the material inlet pipe 29 into the interior of the bushing 7 and axially downwards through the screen plate 10, through its filter element 26, through the pellet of test material, through the filter element 26 of the screen plate 4, through the latter and then through the measuring gas connection 6 to the quantity meter (199 in FIGURE 2). Since the screen plate 10 is held in its pressing position throughout the entire measuring operation, the pellet of test material maintains its dimensions from the moment it is compressed to the prescribed dimension and until the measurement is ended, and thus also maintains its porosity, this providing accurate measurement results.

After completing the measurement, the screen plate 10 is moved by means of the servo motor 13 into 1ts fill1ng and withdrawal position again. The stirrer shaft 42 is also simultaneously carried upwards until the coupling nut 49 is again urged by the compression spring 51 against the bearer plate 46. The cylinder 2 is then lowered by means of the servo motors 37, 38 to such an extent that it can be pivoted by means of the worm 41 and the worm wheel 39 about its journals 31, 32 into an approxlmately horizontal position, and thereafter, by movement of the screen plate 4 by means of the servo motor towards the pellet chamber 20 into its ejection position situated in the region of the opening 17 of the cylinder 2, the pellet is ejected from the cylinder 2. In order to make possible the lowering and pivoting of the cylinder 2, the measuring gas pipe (103 in FIGURE 2) between the measuring gas connection 6 and the quantity meter is made flexible. The measuring gas valve (201 in FIGURE 5) is disposed as close as possible to the pellet chamber 20 in order that the dead space may be kept small.

After ejection of the pellet of test material, the flexible flushing air pipes 66, 67 are connected to a compressed air source (202 in FIGURE 5) and any residues which may still exist in and on the filter elements 26 are removed by being blown out by compressed air. By means of the flushing air valve 68 included in the flushing air pipe 67 of the cylinder 2, the channel defined by this flushing air pipe 67 is closed during the measurement since during this phase, only air flowing through the pellet may pass from the interior of the cylinder 2 into the quantity meter (199 in FIGURE 2) By these measures, a reliable removal of practically all the substance of the test material pellet from the permeability cell is possible, whereby a correct measurement result of the following measurement is obtained, and at the same time the dust formation in the surroundings during the ejection of the pellet is quite considerably reduced. An additional advantage of the permeability cell as illustrated consists in that a pellet of high homogeneity can be prepared therein, and that consequently a pellet of practically any desired size can be compressed, so that the test specimens investigated are truly representative in every case of the ground product being formed at the time.

The quantity meter 199 shown in FIGURE 2 comprises an upper measuring liquid container 101, in the upper region of which is situated a gas zone 102, into which the measuring gas pipe 103 opens, and also a lower measuring liquid container 104. Both measuring liquid containers 101, 104 comprise vertical side walls and horizontal annular bottoms of the same area and are arranged coaxially of one another. The upper measuring liquid container 101 is fixedly arranged, sealed off from the surroundings and is adapted to be connected with its gas zone 102 by way of a vacuum pipe 105 to a vacuum pump 106. Connected into the vacuum pipe 105 is a three-way cock 107, of which the third union is connected to a manometer 108 consisting of a U-shaped tube filled with liquid. The lower measuring liquid container 104 is open upwardly and it rests on the weighing pan 109 of an inclination balance 110. The movement of the weighing pan 109 of the balance which occurs under the action of the weight to be measured is proportional to this weight. A measuring liquid pipe 111 which is coaxial with both measuring liquid containers 101, 104 and is connected fast to the upper measuring liquid container 101 opens into the lower region of the upper measuring liquid container 101 and leads downwardly into the lower measuring liquid container 104. There is measuring liquid in the upper measuring liquid container 101, in the measuring liquid pipe 111 and also in the lower measuring liquid container 104. The level of the measuring liquid in the upper container 101 is indicated at 112, and the measuring liquid level in the lower container 104 is indicated at 113. The measuring liquid in the two measuring liquid containers 101, 104 communicates by way of the measuring liquid pipe 111, of which the lower opening 114 is situated be neath the measuring liquid level 113 in the lower measuring liquid container 104. The vacuum in the gas zone 102 of the upper measuring liquid container 101 is efiective 0n the measuring liquid level 112 therein, on the one hand, and the ambient pressure acts on the measuring liquid level 113 in the lower measuring liquid container 104, on the other hand, in such a way that a measuring liquid column of a height H determined by the upper measuring liquid level 112 and the lower measuring liquid level 113 is maintained. The difference in the heights of the two communicating liquid columns in the manometer 108 also corresponds to this height H of the liquid column.

The balance 110 is so designed that the distance moved by the Weighing pan 109 under the influence of the weight of the measuring liquid quantity which flows from the upper measuring liquid container 101 and through the measuring liquid pipe 111 into the lower measuring liquid container 104 is as large as the sum of the lowering of the measuring liquid level 112 in the upper container 101 and of the simultaneous corresponding rise in the measuring liquid level 113 in the lower container 104. Since both measuring liquid containers 101, 104 comprise vertical side walls and bottoms having the same area. and accordingly a lowering of the liquid level 112 results in a corresponding and equivalent rise of the liquid level 113, the distance moved by the weighing pan 109 when measuring liquid flows from the upper measuring liquid container 101 into the lower measuring liquid container 104 is twice the lowering of the liquid level 112 in the upper measuring liquid container 101 or twice the rise of the liquid level 113 in the lower measuring liquid container 104, respectively.

The balance 110 comprises a sector-shaped indicator element 115, which moves along an arc with the centre point 116 as the weighing pan 109 is moved. The indicator element 115 comprises a peripherically extending slot 117. Arranged on the outside of the sector-shaped indicator element 115 is a photoelectric cell 118 the reception axis of which passes through the point 116. Arranged on the inside of the sector-shaped indicator element 115 and on the reception axis of the photoelectric cell 118 passing through the point 116 is a light source 119, of which the emission axis lies in the receiving axis of the photoelectric cell 118. With the travel of the indicator element 115 corresponding to the movement of the weighing pan 109, the light source 119 is concealed from the photoelectric element 118, always by a solid sector of the indicator element 115, over each end region of the travel of the indicator element, whereas the light source 119 is freed with respect to the photoelectric cell 118 by the slot 117 over a middle part of the travel of the indicator element 115 as established by the slot 117.

The quantity meter 199 as illustrated operates as follows. The measuring gas valve (201 in FIGURE in the measuring gas pipe 103 is closed and the three-way cock 107 is turned to the position shown in the drawing. By means of the vacuum pump 106, the air in the gas zone 102 of the upper measuring liquil container 101 is extracted by suction. As a result, the liquid level 112 in the upper measuring liquid container 101 is raised, and measuring liquid is lifted from the lower measuring liquid container 104 through the measuring liquid pipe 111 into the upper measuring liquid container 101. The threeway cock 107 is then turned to that position in which the gas Zone 102 of the upper liquid container 101 communicates with the manometer 108, but is separated from the vacuum pump 106.

In the gas zone 102 of the upper measuring liquid container 101, there prevails a reduced pressure by comparison with the ambient pressure, said reduced pressure depending on the height H of the liquid column as established by the measuring liquid level 112 and by the measuring liquid level 113. If now the measuring gas valve (201 in FIGURE 5) is opened, outside air flows under the action of this reduced pressure through the sample of material in the cylinder 2 of the permeability cell 99 (FIGURE 1) and into the gas zone 102 of the upper liquid container 101. According to the quantity of gas which filows into the gas zone 102 of the upper measuring liquid container 101, measuring liquid is displaced from this latter container 101 and released through the measuring liquid pipe 111 into the lower measuring liquid container 104.

The measuring liquid flowing from the upper measuring liquid container 101 into the lower measuring liquid container 104 increases the weight of the said container 104, which is resting on the weighing pan 109. Accordingly, the weighing pan 109 descends under the influence of the weight of the supplied measuring liquid.

The quantity of the measuring liquid flowing from the upper measuring liquid container 101 into the lower measuring liquid container 104 corresponds to the quantity of the measuring gas flowing through the permeability cell (99 in FIGURE 1) into the gas zone 102 and the travel of the weighing pan 109 of the balance 110 under the influence of the weight of the added meaeuring liquid corresponds to the travel of the indicator element 115 of the balance 110. Accordingly, the range of the travel of the indicator element 115 determined by the slot 117, over which range the beam from the light source 119 reaches the photoelectric cell 118, corresponds to a prescribed quantity of measuring gas flowing through the permeability cell. The binary signals of the photoelectric cell 118 are delivered to a timing device (216 in FIG- URE 5), which determines the measurement time and converts it into a signal which is proportional to the specific surface of the tested pellet in cm. g. according to Blaine, which conversion is made possible by the fact that the pressure difference produced by the quantity meter and applied to the permeability cell (99 in FIG- URE 1) remains constant throughout the entire measurement period, and this in addition gives reliable measurement results.

The actual measurement of the time only takes place after a certain small quantity of measuring liquid has already flowed from the upper measuring liquid container into the lower measuring liquid container and constant flow conditions have been established in the permeability cell.

In FIGURES 3 and 4, the quantity meter is in each case shown in an operative position in which the indicator element 115 of the balance is in a position in which the light source 119 is just exposed to or concealed from the photoelectric cell 118. In FIGURE 3, there is still a comparatively large quantity of measuring liquid in the upper measuring liquid container 101 and the indicating element of the balance 110 is starting to expose the light source 119 to the photoelectric cell 118 through the slot 117. The height H of the liquid column is determined by the upper measuring liquid level 112 and by the lower measuring liquid level 113. FIGURE 4 shows the quantity meter in an operative position in which such a quantity of measuring liquid has flowed from the upper measuring liquid container 101 into the lower container that the upper measuring liquid level has fallen by the distance S; the original measuring liquid level 112 corresponding to the operative condition according to FIG- URE 3 is represented by a broken line, and the new liquid level at 112'. In corresponding manner, the liquid level in the lower measuring liquid container 104 has risen by the distance A; the original measuring liquid level 113 is represented by a broken line and the new measuring liquid level is indicated at 113. The distances S and A are quantitatively the same as one another. The weighing pan 109 has moved downwardly by the distance W under the influence of the weight of the quantity of measuring liquid which has flowed from the upper container into the lower container, and the indicator element 115 of the balance 110 starts to conceal the light source 119 from the photoelectric cell 118. The distance W corresponds to the sum of the fall of S of the liquid level in the upper measuring liquid container and the rise A of the liquid level in the lower measuring liquid container. This has the result that the height H of the measuring liquid column, which is determined by the upper measuring liquid level and by the lower measuring liquid level, as can be seen from FIGURES 3 and 4, is the same with each height position of the lower measuring liquid container 104 resting on the weighing pan 109, and in fact with each operative position of the quantity meter.

By means of the steps according to application Serial No. 582,105, a quantity meter is obtained in which a pressure difference of practically any desired selectable size can be kept constant with simplest possible means over a measurement period corresponding to any requirement, with which always a quantity of test material which can be chosen to be of practically any size can be tested, and of which the measurement results can be converted directly to the specific surface of the test material in cmP/g. according to Blaine.

In the diagram shown in FIGURE 5, representing a regulating device on a grinding arrangement, there can first of all be seen the permeability cell 99 according to FIGURE 1 and the quantity meter 199 according to FIGURE 2, these parts being interconnected by a measuring gas pipe 103. That section of the measuring gas pipe 103 which is immediately adjacent the permeability cell 99 is made flexible, and the measuring gas valve 201 is arranged between the flexible section and the rigid section of the measuring gas pipe. 202 represents a compressed air source, to which the flushing air pipes 66, 67 of the permeability cell are adapted to be connected.

The reference 203 indicates a cement mill. Leading to the inlet of the mill 203 is a supply pipe 204 for the material, into which is connected a device 205 for dosing the material which is supplied. From the outlet of the mill 203, a ground product pipe 206 leads to the inlet of a sifting device 207, which comprises an arrangement 208 for altering the degree of sitting. In the constructional example as illustrated a conveyor device (not shown) is included in the vertical part of the ground product pipe. The outlet union 209 of the sifting device 207 serving for the coarse material is connected through. a coarse material pipe 210 to that section of the supply pipe 204 which is situated between the dosing device 205 and the inlet to the mill 203. The discharge union 211 for the fine material from the sifting device 207 is connected to a finished product pipe 212, into which is incorporated a partial stream extraction device 213. A pipe 214 which is advantageously constructed as a conveying and/or cooling device leads from the partial stream extraction device 213 to an automatic dosing and weighing device 215, the

outlet of which communicates with the material inlet pipe 29 supplying material to the permeability cell 99.

There is an operative connection 217 between the photoelectric cell (118 in FIGURE 2) of the quantity meter 199 and the timing device 216, and there is also an operative connection 219 between the timing device 216 and the signal input side of a control arrangement 218. From the outlet side of the control arrangement 218, an operative connection 220 leads to the dosing device 205 for the supplied material and an operative connection 221 leads to the device 208 for altering the degree of sifting in the sifting device 207.

A programme emitter is indicated at 222. From this emitter, there is an operative connection 223 with the quantity meter 199, an operative connection 224 with the partial stream extraction device 213 and the automatic dosing and weighing device 215, an operative connection 225 with the permeability cell 99 and an operative connection 226 with the measuring gas valve 201.

The installation shown in FIGURE 5 operates as follows. The dosing device 205 for the supplied material is in the normal position, as is also the device 208 for altering the degree of sifting of the sifting device 207. The supplied material passes through the supply pipe 204 to the mill 203, and the ground product passes through the ground product pipe 206 into the sifting device 207. From the latter, the component stream of coarse material flows back through the coarse material pipe 210 into the mill 203, and the component stream of fine material leaves the installation through the finished product pipe 212.

The screen plates 4, of the permeability cell 99 are disposed in their filling positions, such as. those shown in FIGURE 1, the filling position of one screen plate 10 being also its withdrawal position and the filling position of the other screen plate 4 being also its pressing position.

The programme emitter 222 closes the measuring gas valve 201, connects the gas zone 102 of the quantity meter 199 to the vacuum pump 106 by turning the threeway cock 107 into the position shown in FIGURE 2, until the measuring liquid level 112 in the upper measuring liquid container 101 has reached its upper height position, whereupon the gas zone 102 is again separated from the vacuum pump 106. Thus the quantity meter is ready for carrying out the time measurement. Simultaneously, the programme emitter 222 moves the stirrer blade 43 downwardly into the pellet chamber 20. The permeability cell is then ready for filling (programme phase (a) The programme emitted 222 actuates the partial stream extraction device 213 and the automatic dosing and weighing arrangement 215, and an accurately weighed and prescribed quantity of test material taken from the finished product pipe 212 flows through the material inlet pipe 29 into the pellet chamber of the permeability cell 99, the said test material having been cooled in the cooling arrangement included in the pipe 214. The programme emitter 222 simultaneously lifts the stirrer blade 43 from the pellet chamber 20 and rotates it about the axis of the stirrer shaft 42, and the test material in the pellet chamber 20 is homogenised. As a result, the permeability cell 99 is ready to compress the pellet (programme phase (b) The programme emitter 222 moves the screen plate 10 of the permeability cell 99 from its filling and withdrawal position as shown in FIGURE 1 towards the pellet chamber 20 and into its pressing position 19, the other screen plate 4 remaining in its position shown in FIGURE 1 which is both the filling and pressing position, and the test material is compressed into the pellet. The screen plate 10 is thereafter retained in its pressing position 19. The permeability cell 99 is then also ready for carrying out the time measurement (programme phase (0)).

The programme emitter 222 opens the measuring gas valve 201 and the time measurement is initiated and is effected in the manner set out above (programme phase (d)).

Since the duration of the time measurement is indefinite, the programme emitter must provide a time sufficient in all cases occurring in practice until the commencement of the following programme phase (e). However, it is also possible to provide the programme emitter with a special measurement programme emitter, which is set in operation by the programme emitter and which in its turn makes the latter inoperative after commencement of the measuring programme and sets it in operation again after completing the measurement programme, whereupon the programme emitter in its turn renders the measuring programme emitter inoperative.

The binary signals supplied during the time measurement (programme phase (d)) by the photoelectric cell 118 (FIGURE 2) of the quantity meter 199 to the timing device 216 are processed by the latter into a measurement time result and converted in analogue manner into a signal proportional to the specific surface of the tested pellet in cm. g. according to Blaine. By means of this signal, the device 208 for altering the degree of sifting in the sifter 207 is so controlled by the connection 221 that when the prescribed time corresponding to the prescribed specific surface of the test material is exceeded by the measured time, the degree of sitting of the sifter 207 is increased and as a consequence a smaller component stream of coarse material passes through the coarse material pipe 210 to the inlet of the mill 203, whereby the degree of grinding of the mill 203 is reduced, and that conversely, when the prescribed time is not reached by the measured time, the degree of sifting of the sifter is reduced and consequently a larger stream of coarse material flows back into the mill, whereby the degree of grinding thereof is increased. The closing device 205 for the supply material, which device could also be omitted in the constructional example as shown, is likewise controlled by the control device through the connection 220 in corresponding manner, it preferably only being used for the coarse control when deviations in the measured time from the prescribed time occur which are of an extreme size. The control device 218 can also be operatively connected to a warning arrangement or to an arrangement which shuts down the entire installation and actuate these arrangements when there are extreme deviations from the nominal value. With a mill operated in an open circuit, where there is no sifting and return of a stream of coarse material into the mill, the influencing of the degree of grinding of the mill is effected solely by the dosing device for the supply material. However, also any other device for influencing the degree of grinding of the grinding arrangement can be controlled by the control arrangement 218.

After completing the time measurement (programme phase (d) the programme emitter 222 moves the screen plate 10 of the permeability cell 99 back to its filling and withdrawal position, lowers the cylinder 2 from its upper position adjacent the bushing 7, as shown in FIGURE 1, and pivots the same into a substantially horizontal posi- 13 tion. The programme emitter then moves the other screen plate 4 from its filling and pressing position towards the pellet chamber 20 and into its ejection position 17, whereby the pellet is ejected and reliably drops down. The programme emitter 222 then connects the flushing air pipes 66, 67 to the compressed air source 202 and opens the flushing air valve 68 of the flushing air pipe 67, whereby the residues of material in and on the filter elements 26 are removed by means of the compressed air by a blowing action, whereupon the flushing air pipes 66, 67 are separated from the compressed air source 202 and the flushing air valve 68 is closed, the cylinder 2 is swung into the vertical position and is raised into its upper position as shown in FIGURE 1 (programme phase (e) The installation is then ready for a new programme.

The programme phases a and e take place concurrently. This permits of shortening the time necessary for carrying out the programme. A further shortening of this time is achieved by the fact that, as set forth, the programme emitter is provided with a separate measurement programme emitter, whereby it is possible, for the programme phase ti, the time measurement, not to take more time than this measurement needs, and the programme phase e, the emptying of the pellet chamber 20, can be initiated immediately after elapse of the time effectively required for the time measurement. This shortening of the time required for the programme makes it possible for the measurements to follow closely after one another and produces a good continuity of the regulating procedure.

With the regulating device according to the invention, it is possible to maintain a prescribed specific surface of the finished product within narrow limits by continuous control of the device which influences the degree of grinding of the grinding arrangement.

In an installation of the type set forth, it was possible to carry out in one hour 20 permeability measurements of cement pellets weighing 250 g., the measurement results being within a very close range. The time sequence corresponds to a high degree to the requirements of continuous control and the size of the pellets guarantees that the quantity of material which is examined with each measurement is in every case truly representative.

The installation as described can also be combined with a computer having a datum store, which integrates a prescribed number of measurement results, and in this way an even better regulation can be produced. By means of a computer with datum store it is in addition possible to construct a central control system for a complete cement factory.

' We claim:

1. A grinding arrangement havng a regulating device for maintaining a prescribed specific surface of the finished product, comprising in combination: an apparatus for measuring the permeability of samples of said finished product having a permeability cell for receiving said samples; and a quantity meter serving to measure the quantities of measuring gas flowing through said samples in said cell, said permeability cell including:

(a) a base plate,

(b) a hollow cylinder, closed at the lower end and open at the upper end, mounted beneath the base plate and arranged to receive the test material,

(c) a lower screen plate extending entirely across said cylinder perpendicular to the cylinder axis and shiftable axially between two limiting positions, namely a pressing position situated near the lower end of the cylinder and an ejection position in which the upper face of the plate is in the region of the upper end of the cylinder,

(d) means connected to the plate to shift it between said positions,

(e) an upper screen plate of the same size as the lower screen plate, mounted on the base plate coaxially and parallel with the lower screen plate and shiftable axially of the cylinder between a filling position, in

which it is above the upper end of the cylinder, and a pressing position, in which it is in the cylinder and spaced a prescribed distance above the lower screen plate,

(f) means for supplying material to be tested to the open end of the cylinder when the lower screen plate is in pressing position and the upper screen plate is in filling position, and

(g) flow connections to said cylinder above and below the upper and lower screen plates, respectively, when they are in pressing positions;

said quantity meter comprising:

(A) first and second containers each of which contains liquid to provide therein liquid spaces, the first container being closed and only partly filled with liquid to define therein a gas space,

(B) a liquid-filled transfer path extending between said liquid spaces, the ends of said transfer path being always covered by liquid in the containers,

(C) a gas flow path receiving one of said samples and having one end in communication with the gas space of the closed container and having a constant gas pressure at its opposite end,

(D) the liquid in said second container being subject to a gas pressure,

(E) means establishing in the gas space of the closed container a pressure different from said constant pressure existing at the end of said flow path, thereby establishing the positions of the liquid levels in said containers relatively to one another,

(F) means positioning one of said containers so as to maintain unchanged the positions of the liquid levels relatively to one another when gas flows through said sample, and

(G) means measuring the displacement of liquid from one container to the other;

a measuring gas pipe including a measuring gas valve connecting the gas space of said closed container of said quantity meter to one of said flow connections of said cylinder of said permeability cell; a device for influencing the degree of grinding of the grinding arrangement; a timing means measuring the time required for a prescribed quantity of measuring liquid to be displaced from one container to the other and converting the measured time into a signal corresponding to the specific surface of the material sample traversed by measuring gas; a control means responsive to said signal and controlling said device in such a way that when a prescribed time is exceeded by the measured time, said device is actuated in the sense to reduce the degree of grinding, whereas when this prescribed time is not reached, the device is actuated in the sense to increase the degree of grinding; a device for extracting a partal stream of the finished product for the formation of said samples; an automatic dosing and weighing device for said samples connected, on the input side, to the partial stream output side of said extracting device, and, on the output side, to said sample supply pipe of said permeability cell.

2. The combination defined in claim 1, in which said device for influencing the degree of grinding of the grinding arrangement is constructed as a device for dosing the material supply to the grinding arrangement.

3. The combination defined in claim 1, in which said device for influencing the degree of grinding of the grinding arrangement is constructed as a sifting device having adjustable means for recirculating a coarse fraction of the ground product to the material supply.

4. The combination defined in claim 1, comprising a programme emitter, which is operatively connected to said permeability cell, to said quantity meter, to said measuring gas valve, to said device for extracting a partial stream and to said automatic dosing and weighing device in such a manner and so constructed as to control the following programme:

(a) in the filling positions of said screen plates of said permeability cell, closing said measuring gas valve, connecting said gas space of said closed measuring liquid container of said quantity meter to said means establishing a pressure in the closed container and disconnecting said gas space from that means after the displacement of a prescribed amount of liquid from one container to the other;

(b) actuating said partial stream extraction device and said automatic dosing and weighing device and thereby filling said cylinder of said permeability cell with a sample of test material;

(c) moving said upper screen plate into its pressing position and thereby compressing said sample to a pellet, and also holding said screen plates in said pressing positions;

((1) opening said measuring gas valve and thereby initiating the timing;

(c) after completion of the timing, withdrawing said upper screen plate into its filling position and moving said lower screen plate towards said cylinder into its ejecting position to eject said pellet, and also returning said lower screen plate back into its filling position.

5. The combination defined in claim 4, in which said programme emitter is so constructed that said phases a and e of said programme take place concurrently.

6. The combination defined in claim 4, in which the permeability cell includes a stirrer blade for homogenizing the material to be tested before its being pressed, arranged between said screen plates coaxially with said cylinder, extending perpendicularly to the cylinder axis and covering approximately the entire internal diameter of said cylinder; said stirrer blade having a driving shaft extending upwardly so as to penetrate said upper screen plate and mounted for rotation about the cylinder axis while being axially shiftable; means for rotating and axially moving said shaft so as to displace said stirrer blade within the space left between said upper and lower screen plates; and means for the synchronous axial displacement of said upper screen plate and said stirrer blade axially adjacent one another; and in which said programme emitter is so constructed as to control the following amplified programme phases (a) and (b):

(a) in the filling positions of said screen plates of said permeability cell, closing said measuring gas valve, connecting said gas space of said closed measuring liquid container of said quantity meter to said means establishing a pressure in the closed container and disconnecting said gas space from that means after the displacement of a prescribed amount of liquid from one container to the other, and also simultaneously lowering said stirrer blade into said cylinder of said permeability cell;

(b) actuating said partial stream extraction device and said automatic dosing and weighing device and thereby filling said cylinder of said permeability cell with a sample of test material and also simultaneously lifting said stirrer blade from said cylinder with simultaneous rotation thereof about the axis of said stirrer shaft, and thereby homogenizing the test material in said cylinder.

7. The combination defined in claim 4, in which said permeability cell comprises a stationary bushing with vertical axis forming an abutment for the open end of said cylinder and serving as a guide for said upper screen plate; and in which means for lowering said cylinder away from said bushing and for swiveling said cylinder about a horizontal axis are provided so as to allow ejection of the tested pellet of material; and in which flushing air pipes are provided which are adapted to connect the spaces on those sides of said screen plates which are remote from said cylinder to a source of compressed air, the flushing air pipe associated with said lower screen plate including a flushing gas valve; and in which said programme emitter is so constructed as to control the following amplified programme phase corresponding to phase (e):

(a) after completion of the timing, moving of said upper screen plate from its pressing position back into its filling and withdrawal position, lowering said cylinder from its upper position adjacent said bush ing and pivoting it into a substantially horizontal position, moving said lower screen plate from its filling and pressing position towards said cylinder and into its ejection position and thereby causing ejection of the pellet, connecting said flushing air pipes to said source of compressed air and opening said flushing air valve and thereby removing the residues of material by flowing, separating said flushing air pipes from said source of compressed air and closing said flushing air valve, pivoting said cylinder into a vertical position and also moving said lower screen plate back into its filling and pressing position,

References Cited UNITED STATES PATENTS 1,990,178 2/1935 Frisch 24 l34 2,365,496 12/1944 Shaw.

2,509,905 5/1950 Burris 73--38 2,517,451 8/1950 Sorteberg 24-l34 X 2,534,718 12/1950 Leas 7338 2,618,151 11/1952 Leas 7338 2,659,433 11/1953 Brown 73-38 X 3,039,293 6/1962 Reddick 7338 3,055,208 9/1962 Gallus 736l.4 X 3,358,938 12/ 1967 Brown 24l-34 X ROBERT C. RIORDON, Primary Examiner D, G. KELLY, Assistant Examiner 

